ABC News recently toured the Metropolitan Wellness Center, one of the district's three soon-to-open shops, located on Capitol Hill.

While pot products have yet to hit shelves – the shop is still awaiting a license from the district – general manager Vanessa West said they will soon offer multiple varieties of cannabis, paraphernalia and a mix of pot-infused products, including brownies, cookies and drinks.

West, a veteran operator of dispensaries in California who admits she "smoked a little grass in college," said the sleek, modern set-up of her "product selection and payment room" underscores a serious focus on patients and treating their pain.

"When we find out what a patient's symptoms are, we can make a recommendation about what the best strain is for them and what the best possible route for ingesting that strain is," she said.

"Forget about the recreational part for a second," she says to skeptics. "Listen to how cannabis has changed patients' lives for the better."

Only employees and patients registered with the District of Columbia Department of Health will be allowed inside the dispensary once weed sales officially commence. The shop will effectively go on lockdown, protected by a high-tech security system of a dozen cameras and motion sensors keeping watch.

"This is sort of a delicate business," West said. "It's like a bank or a high end jewelry store. We want to protect the product and the people that are inside this building."

Under district law, no one is allowed to consume pot on the premises, West said. Approved users are required to head directly home after making their purchases.

The rules for obtaining legal access to the drug are equally stringent. A prospective patient must be a district resident with one of the few qualifying diseases, such as AIDS, glaucoma or multiple sclerosis. A doctor must formally recommend the drug, and that recommendation must be certified by the Department of Health. Each patient must also submit an application and pay a license fee.

"It's a pretty difficult process, but it sort of needs to be," said West. "You don't want to create a free for all."

The dispensaries in D.C. will remain illegal under federal law, which still bans the cultivation and sale of marijuana as a dangerous and addictive "Schedule I" drug under the Controlled Substances Act. Officially, marijuana is classified has having "no currently accepted medical use in treatment in the U.S."

The headquarters for the Justice Department, the federal agency responsible for enforcing federal law, is located just four miles from the Metropolitan Wellness Center.

West says she's not worried about a raid.

"History has shown that if you are a dispensary operating in a state that is transparent and heavily regulated, the federal government is not interested in intervening," she said.

Support for Legalizing Pot Grows

Medical marijuana is now allowed in 18 states plus the District of Columbia. In November, voters in Colorado and Washington took the movement further, endorsing the sale of marijuana without a prescription for recreational purposes. Both states are establishing regulatory regimens for pot similar to alcohol.

A poll released last month by the Pew Research Center found for the first time a majority of Americans now favor full legalization of marijuana. Fifty-two percent favor decriminalization, with 45 percent opposed.

The level of support is a landmark shift from 40 years ago when just 12 percent backed legalized pot, according to Gallup.

In light of the trend, President Obama told ABC News' Barbara Walters in December that he's re-thinking federal prosecution of some marijuana users.

"It does not make sense, from a prioritization point of view, for us to focus on recreational drug users in a state that has already said that under state laws that's legal," Obama said.

"We've got bigger fish to fry," he added.

The big question now for pro-pot states: Will the Justice Department spoil plans for dozens of new dispensaries, and a potential bonanza of millions in taxes and fees?

The Department, which is reviewing the new Colorado and Washington marijuana laws, has yet to formally decide whether or not they will be challenged in court.

Meanwhile, lawmakers from those states have re-invigorated legislative efforts to repeal or weaken the federal ban on pot. So far this year, seven bills dealing with marijuana have been introduced in the U.S. House, including one that would entirely decriminalize the drug.

All of the bills face an uphill climb, which means for now at least, the new D.C. dispensaries will remain at odds with the law.